Scientists create whitest paint. Could eliminate need for A/C, combat warming | Hacker News Reader

Scientists create whitest paint. Could eliminate need for A/C, combat warming

usatoday.com

16 pointsnathandaly8 comments

I read the abstract of their paper and I can tell that the paint they created will be completely useless in the real world. No paint company would be interested in this.

They used a 60% volume concentration of barium sulfate. This is very high for an exterior paint and pretty much guarantees that it will have a very poor mechanical durability. The high amount of pigment with make the paint matt and attract dirt easily. Barium sulfate doesn't absorb UV so the paint will be degraded by UV easily.

You could coat the backside of a pane of glass with this. In fact, why not just cover your roof with mirrors, as that is effectivly what is created.

Do mirrors ambiently cool the surface they're attached to in the same way as is described in the article? I wondered the same thing when reading it.

Hrmm this article here makes it sound like you can also do this with a mirror, but it implies that not any mirror would suffice, and that they had to design a special mirror surface to get one that also radiates heat at a wavelength that will let it escape the atmosphere:

http://theguardian.com/science/2014/nov/26/mirrors-air-condi...

> The first layer is reflective silver. On top of this are alternating layers of silicon dioxide and hafnium oxide. These layers improve the reflectivity, but also turn the mirror into a thermal radiator. When silicon dioxide heats up, it radiates the heat as infrared light at a wavelength of around 10 micrometres. Since there is very little in the atmosphere that absorbs at that wavelength, the heat passes straight out to space. The total thickness of the mirror is around two micrometres, or two thousandths of a millimetre.

> Fan puts the installed cost of mirrors at between $20 and $70 per square metre and calculates an annual electricity saving of 100MWh per year on a three storey building

HN discussion here: https://news.ycombinator.com/item?id=28583676

Because the paint absorbs less heat from the sun than it emits, a surface coated with this paint is cooled below the surrounding temperature without consuming power.

Using this new paint to cover a roof area of about 1,000 square feet could result in a cooling power of 10 kilowatts. “That’s more powerful than the air conditioners used by most houses,”

I wonder how often it’d need to be cleaned to maintain the cooling effect.

With the amount of pigment they used to achieve that level of whiteness there is gonna be no was to clean this without damaging the coating.

Ambiently cools by emitting more heat than it absorbs -- pretty nifty!

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